Method and system for conveying backhaul link information for intelligent selection of a mesh access point

ABSTRACT

A method and system for conveying backhaul link information for intelligent selection of a mesh access point (MAP) in a mesh network are disclosed. The mesh network includes a plurality of MAPs. The MAPs send backhaul link information regarding backhaul connections between each MAP and any interconnections in the mesh network to a wireless transmit/receive unit (WTRU). The WTRU then determines a performance value with respect to the MAPs based on the backhaul link information and selects one of the MAPs to associate with based on the performance value. The WTRU may send information about interconnection needs of the WTRU to the MAPs, and the MAPs may generate the backhaul link information based on the interconnection needs of the WTRU.

CROSS REFERENCE TO RELATED APPLICATION

This application claims the benefit of U.S. provisional application No.60/690,244 filed Jun. 14, 2005, which is incorporated by reference as iffully set forth.

FIELD OF INVENTION

The present invention is related to a wireless communication system.More particularly, the present invention is related to a method andsystem for conveying backhaul link information for intelligent selectionof a mesh access point (MAP) in a mesh network.

BACKGROUND

A conventional wireless network includes a set of access points (APs),(also known as base stations), each of which is connected to a backhaulnetwork. In certain deployments, the cost of directly connecting a givenAP to the backhaul network is too high. Thus, indirectly connecting theAP to the backhaul network may be more attractive. This indirectconnection is typically accomplished by relaying information to and fromneighboring APs in a mesh network. This is referred to as a mesharchitecture.

A mesh network is a local area network (LAN) including a plurality ofmesh points (MPs). The connections between the MPs may be wired orwireless. The points of interconnection between a mesh system and anon-mesh system are referred to as portals. A mesh system with multipleportals is referred to as a multi-portal mesh system. A node capable ofboth AP and MP functionalities is referred to as a mesh access point(MAP). FIG. 1 shows an exemplary mesh network 100. The mesh network 100includes a plurality of MPs 102, a plurality of MAPs 104 and a meshportal 106. The MPs 102 serve as forwarding and relaying nodes in themesh network 100. The MPs 102 receive traffic on incoming links andforward the traffic on outgoing links. The MAPs 104 are also MPs with aninterface to provide radio access to a plurality of wirelesstransmit/receive units (WTRUs) 108 to provide wireless services in acertain geographic area. The mesh portal 106 provides connectivity to abackbone network 110, (such as the Internet), in the mesh network 100.Thus, the mesh portal 106 acts as an MP with a special interface to thebackbone network 110. Each of the WTRUs 108 communicates with anotherWTRU in the mesh network 100, or to the backbone network 110, via theMAPs 104 and the mesh portal 106. The MAPs 104 forward the trafficgenerated by the WTRUs 108 to another MAP 104 or the mesh portal 106 byrelaying the traffic via intermittent MPs 102 and/or MAPs 104.

A mesh network is reliable and offers redundancy. Even if one or more ofthe MPs can no longer operate, the rest of the MPs can still communicatewith each other, directly or through one or more intermediate MPs suchthat the network may function properly. Other considerations, such asease and speed of deployment, are advantages of the mesh network since amesh network may be deployed without having to provide direct backhaullinks and interconnection modules for each MP in the mesh network.

In conventional non-mesh wireless communication systems, a WTRU needs toestimate which AP will provide the best communication link to the WTRU.WTRUs typically use the following information and methods fordetermining which AP to associate with:

1) the identity of the network of which a candidate AP is a part of,(e.g., in IEEE 802.11 systems, this identity corresponds to the serviceset identifier (SSID) provided to the WTRUs in a beacon frame or a proberesponse frame);

2) the capabilities of the candidate AP including information regardingwhich services the AP supports, (e.g., in IEEE 802.11 systems, thiscapability information is included in a capability information field ina beacon frame or a probe response frame); or

3) the expected achievable data throughput, (e.g., the WTRU may estimatethe expected throughput by measuring a received power it perceives froman AP on beacon frames, probe response frames or any other frames). Thereceived power, a signal-to-interference-plus-noise-ratio (SINR) orsimilar measurements typically sets the maximum rate the WTRU mayachieve on a given communication link. The WTRU can also use channeloccupancy or channel load measurements, whether measured by the WTRU orcollected from the AP, to refine the expected throughput estimate.

The above-described information and methods utilized to select an APthat a WTRU should associate with are no longer adequate in a meshnetwork. For example, in a conventional infrastructure mode WLAN, thethroughput achieved on a given WTRU-AP link depends only on thecharacteristics of that particular radio link between the AP and theWTRU, (i.e., channel occupancy, received power, a signal-to-interferenceand noise ratio (SINR), or the like). However, in a mesh network, thethroughput not only depends on the characteristics of the radio linkbetween a given WTRU and its serving MAP, but it also depends on thecharacteristics of the radio link(s) between the serving MAP and otherintermediate MPs that forward the traffic from the serving MAP to themesh portal.

FIG. 2 illustrates an example of an intelligent association problem in aconventional mesh network 200. In this example, the mesh network 200comprises three MAPs 201, 202 and 203. The MAPs 201 and 203 are meshportals which have connectivity to the Internet 230 via a router 220.The interconnection resources of the MAPs 201, 203 may beEthernet-based. In this example, the MAP 202 and the MAP 203 arecandidate MAPs for a WTRU 210. If the WTRU 210 is associated with theMAP 102, traffic to/from the Internet 230 is routed via radio links L2and L1 via the MAP 201. If the WTRU 210 is associated with the MAP 203,the traffic to/from the Internet 230 is routed via radio link L3. Anexemplary set of radio link characteristics for the radio links L1, L2and L3 is illustrated in Table 1 below.

TABLE 1 Radio Transmission Single-link link Nodes SNR rate throughput L1MAP1 MAP2 10 dB 12 Mbps  5 Mbps L2 STA MAP2 35 dB 54 Mbps 20 Mbps L3 STAMAP3 20 dB 36 Mbps 15 Mbps

According to Table 1, if the WTRU 210 associates with the MAP 203, thethroughput would be 15 Mbps. However, if the WTRU 210 associates withthe MAP 202, the throughput would be determined by the combination ofdata throughput of two links L1, L2, which is typically estimated asfollows:1/(1/troughput_L1+1/throughput_L2).  Equation (1)

Applying Equation (1) to radio links L1 and L2, the combined throughputwould be 1/(⅕+ 1/20) or 4 Mbps. From this calculation it becomes evidentthat the WTRU 210 will experience a better throughput by associatingwith the MAP 203 than by associating with the MAP 202. From theperspective of the overall mesh network 200, the preferred associationof the WTRU 210 is to the MAP 203. The radio connection of L1 and L2between the WTRU 210 and the MAP 201 offers 3.75 times (i.e., 15 Mbps/4Mbps) less throughput than the multi-hop radio connection between theWTRU 210 and the MAP 203.

According to the prior art, in the foregoing example, the radio link L2between the WTRU 210 and the MAP 202 seems more attractive, (in terms ofsignal-to-noise ratio (SNR), estimated achievable transmission rate,estimate single-link throughput, channel occupancy, or the like), thanthe radio link L3 between the WTRU 210 and the MAP 203. In the priorart, since the WTRU 210 has no means of knowing that associating withthe MAP 203 will result in a better throughput than associating with theMAP 202, the WTRU 210 may end up with a less favorable MAP.

Accordingly, it is desirable to have a method and apparatus for enablinga WTRU to intelligently associate with a MAP in a mesh network.

SUMMARY

The present invention is related to a method and system for conveyingbackhaul link information for intelligent selection of a mesh accesspoint (MAP) in a mesh network. The mesh network includes a plurality ofMAPs. The MAPs send backhaul link information regarding backhaulconnections between each MAP and any interconnections in the meshnetwork to a WTRU. The WTRU then determines a performance value withrespect to the MAPs based on the backhaul link information and selectsone of the MAPs to associate with based on the performance value. TheWTRU may send information about interconnection needs of the WTRU to theMAPs, and the MAPs may generate the backhaul link information based onthe interconnection needs of the WTRU.

In prior art systems, a WTRU may associate to a MAP that will result inworse performance than other MAPs because the WTRU has no means ofknowing about the performance of the different radio links that are usedto convey its traffic to/from a desired mesh portal. In accordance withthe present invention, a WTRU may estimate the expected throughput forthe end-to-end connection, which allows the WTRU to associate to a MAPthat provides the best performance from the point of view of both theWTRU and the overall system.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an exemplary block diagram of a conventional mesh network.

FIG. 2 illustrates an example of an intelligent association problem in aconventional mesh network.

FIG. 3 is a signaling diagram between a MAP and a WTRU for selecting aMAP in a mesh network in accordance with an embodiment of the presentinvention.

FIG. 4 is a signaling diagram between a MAP and a WTRU for selecting aMAP in a mesh network in accordance with another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

When referred to hereafter, the terminology “WTRU” includes but is notlimited to a user equipment, a mobile station, a fixed or mobilesubscriber unit, a pager, or any other type of device capable ofoperating in a wireless environment. When referred to hereafter, theterminology “MAP” includes but is not limited to a base station, aNode-B, a site controller, an access point or any other type ofinterfacing device that has a mesh functionality in a wirelessenvironment.

The features of the present invention may be incorporated into anintegrated circuit (IC) or be configured in a circuit comprising amultitude of interconnecting components.

FIG. 3 is a signaling diagram between MAPs 302 a-302 n and a WTRU 304for selecting one of the MAPs 302 a-302 n to associate with inaccordance with an embodiment of the present invention. At least one ofthe MAPs 302 a-302 n in the mesh network sends backhaul link informationregarding backhaul connections between each of the MAPs 302 a-302 n andany interconnections in the mesh network to the WTRU 304 (step 312). Thebackhaul link information may be broadcast, (e.g., via a beacon frame),in a region covered by each of the MAPs 302 a-302 n or may be sent viaunicast, (e.g., via a probe response frame), to a particular WTRU. Ofcourse, other methods known to those skilled in the art may also be usedto provide backhaul link information to WTRUs, in accordance with thepresent invention.

The backhaul link information that each of the MAPs 302 a-302 n sends tothe WTRU 304 includes, but is not limited to: 1) the number of portalseach MAP 302 a-302 n can communicate with; 2) the number of routesseparated from each MAP 302 a-302 n to a mesh portal; 3) the number ofhops and/or the number of MPs per route separated from each MAP 302a-302 n to a mesh portal; 4) an average transmission rate used on eachradio link, or by each of the different MPs, involved in the forwardingof packets between each MAP 302 a-302 n and a mesh portal; 5) anestimated throughput per radio link, or per MP, involved in theforwarding of packets between each MAP 302 a-302 n and a mesh portal; 6)channel occupancy perceived on each radio link, or by each MP, involvedin the forwarding of packets between each MAP 302 a-302 n and a meshportal; 7) radio resources allocated on each radio link, or by each MP,involved in the forwarding of packets between each of the MAPs 302 a-302n and a mesh portal; 8) quality experienced on each radio link, or byeach MP, involved in the forwarding of packets between each of the MAPs302 a-302 n and a mesh portal, (e.g., queued time, medium access delay,time jitter, time latency, a packet error rate); and 9) any performancemetric comprising a weighted sum or any other combination of theabove-mentioned metrics.

The WTRU 304 then determines an end-to-end performance value withrespect to each of the MAPs 302 a-302 n based on the received backhaullink information (step 314). The backhaul link information enables theWTRU 304 to intelligently estimate the end-to-end performance valueafter associating with a particular MAP 302 a-302 n. For example, theWTRU 304 may estimate a data throughput that the WTRU 304 can expectalong an end-to-end radio connection by associating with a particularMAP 302 a-302 n.

The WTRU 304 then selects one of the MAPs 302 a-302 n to associate withbased on the performance value (step 316). Unlike conventional methodsof making an association decision, the decision is not solely based onthe expected performance, (e.g., expected throughput), of the directradio link between the WTRU 304 and a particular MAP 302 a-302 n, but onthe end-to-end performance value, such as end-to-end throughput.

FIG. 4 is a signaling diagram between at least one MAP 402 a-402 n and aWTRU 404 for selecting one of the MAPs 402 a-402 n in accordance withanother embodiment of the present invention. In this embodiment, theMAPs 402 a-402 n generate the backhaul link information based oninterconnection needs of the WTRU 404 in terms of a particular meshportal or a particular MAP 402 a-402 n. As the interconnection needs mayvary from one WTRU 404 to another, it may be desirable for a MAP 402a-402 n to know the interconnection needs, (e.g., a desired meshportal), of a given WTRU 404 in order for the MAP 402 a-402 n tocommunicate backhaul link information that is relevant to the WTRU 404.

The WTRU 404 sends a message for interconnection needs of the WTRU 404to at least one MAP 402 a-402 n (step 412). Information included in themessage includes, but is not limited to: 1) an IP address that the WTRU404 desires to connect with; 2) a medium access control (MAC) address ofthe nodes that the WTRU 404 wants to connect with; 3) an addressallowing a MAP 402 a-402 n to identify a given mesh portal from othermesh portals; 4) a subnet address that the WTRU 404 wants to connectwith; and 5) a predetermined code or flag which allows a MAP 402 a-402 nto determine the connectivity needs of the WTRU 404. The message may besent via a probe request frame, a special control frame, as part of thebody of a data frame, a broadcast frame, or any other type of frames.

Each of the MAPs 402 a-402 n generates backhaul link information basedon the interconnection needs of the WTRU 404 (step 414). For example, aWTRU that needs to connect to the Internet may be interested in choosinga MAP that offers the best route to a mesh portal interconnecting themesh network to the Internet. On the other hand, a WTRU located in agiven basic service set (BSS) that is interested in communicating withanother WTRU located in a neighboring BSS would choose a MAP offeringthe best route to the a base station, (or a MAP), serving that neighborBSS.

Each of the MAPs 402 a-402 n then sends the backhaul link information tothe WTRU 404 (step 416). The backhaul link information may be broadcast,(e.g., via a beacon frame), or may be unicast directly to the WTRU 404,(e.g., via a probe response frame).

The WTRU 404 then determines an end-to-end performance value withrespect to each of the MAPs 402 a-402 n based on the received backhaullink information (step 418). The backhaul link information enables theWTRU 404 to intelligently estimate an end-to-end performance value afterassociating with a particular MAP 402 a-402 n. For example, the WTRU 404may estimate a data throughput the WTRU 404 can expect along anend-to-end radio connection by associating with a particular MAP 402a-402 n. The WTRU 404 then selects one of the MAPs 402 a-402 n toassociate with based on the performance value (step 420).

It is also possible for the MAP to communicate to the WTRU all backhaullink information without any regards to the interconnection needs of theWTRU.

Although the features and elements of the present invention aredescribed in the preferred embodiments in particular combinations, eachfeature or element can be used alone without the other features andelements of the preferred embodiments or in various combinations with orwithout other features and elements of the present invention.

1. A method for use in a wireless transmit/receive unit (WTRU) forassociating with a mesh access point (MAP), the method comprising:receiving backhaul link information including an estimated throughputrelated to the MAP and a number of hops separating the MAP and a meshportal, wherein the number of hops is a number of intervening MAPsbetween the MAP and the mesh portal; determining an end-to-endperformance value based on the backhaul link information received;associating with the MAP based on the end-to-end performance value; andtransmitting information about interconnection requirements via at leastone of a probe request frame, a special control frame, a data frame, ora broadcast frame.
 2. The method of claim 1, further comprising:determining a throughput as the end-to-end performance value.
 3. Themethod of claim 1 wherein the information about interconnectionrequirements includes at least one of an Internet Protocol (IP) addressof a node with which the WTRU desires to connect, a medium accesscontrol (MAC) address of a node with which the WTRU desires to connect,or a subnet address with which the WTRU desires to connect.
 4. Awireless transmit/receive unit (WTRU) comprising: a receiver configuredto receive backhaul link information including an estimated throughputrelated to a mesh access point (MAP) and a number of hops separating theMAP and a mesh portal, wherein the number of hops is a number ofintervening MAPs between the MAP and the mesh portal; a processorconfigured to determine an end-to-end performance value based on thebackhaul link information received and to associate the WTRU with theMAP based on the end-to-end performance value; and a transmitterconfigured to send information about interconnection requirements via atleast one of a probe request frame, a special control frame, a dataframe, or a broadcast frame.
 5. The WTRU of claim 4 wherein theprocessor is further configured to determine a throughput as theend-to-end performance value.
 6. The WTRU of claim 4 wherein theinformation about interconnection requirements includes at least one ofan Internet Protocol (IP) address of a node with which the WTRU desiresto connect, a medium access control (MAC) address of a node with whichthe WTRU desires to connect, or a subnet address with which the WTRUdesires to connect.
 7. A mesh access point (MAP) comprising: a receiverconfigured to receive information about interconnection requirementsincluding an Internet Protocol (IP) address via at least one of a proberequest frame, a special control frame, a data frame, or a broadcastframe; a processor configured to generate a backhaul link informationincluding a number of hops, wherein the number of hops is a number ofintervening MAPs between a first MAP and a mesh portal, based on theinterconnection requirement information; and a transmitter configured totransmit the backhaul link information; wherein the backhaul linkinformation includes at least one of a number of mesh portals with whichMAP communicates, the number of routes separating the MAP to a meshportal, and mesh points (MPs) per route separating the MAP to the meshportal, an average transmission rate on each link between the MAP andthe mesh portal, an estimated throughput between the MAP and the meshportal, channel occupancy perceived on each link between the MAP and themesh portal, radio resources allocated on each link between the MAP andthe mesh portal, and perceive quality of each link between the MAP andthe mesh portal.
 8. The MAP of claim 7 wherein the transmitter isfurther configured to broadcast the backhaul link information via abeacon frame.
 9. The MAP of claim 7 wherein the transmitter is furtherconfigured to transmit the backhaul link information via a proberesponse frame.